Soil Bearing Capacity and Load Calculator
Calculate the ultimate and allowable bearing capacity of soil using Terzaghi's General Bearing Capacity Equation, and determine the maximum allowable structural load for a specified footing area.
Soil Properties
Use 0 for purely granular (cohesionless) soils. Typical range: 0° (soft clay) to 45° (dense gravel). Typical range: 14–22 kN/m³.Footing Geometry
Depth from ground surface to footing base. Shorter dimension of the footing. Longer dimension. Set equal to B for square/circular footings.Safety & Load
Typical value: 2.5–3.0 for foundations. Leave blank to skip load check.Results will appear here.
Formulas Used
Terzaghi-Meyerhof General Bearing Capacity Equation:
qu = c · Nc · sc + γ · Df · Nq · sq + 0.5 · γ · B · Nγ · sγ
Bearing Capacity Factors:
Nq = eπ·tan φ · tan²(45 + φ/2)Nc = (Nq − 1) · cot φ(= 5.14 when φ = 0°)Nγ = 2 · (Nq + 1) · tan φ(Meyerhof)
Shape Factors (De Beer / Meyerhof):
- Strip: sc = sq = sγ = 1.0
- Circular: sc = 1.3, sq = 1.0, sγ = 0.6
- Rectangular: sc = 1 + 0.2(B/L), sq = 1 + (B/L)·tan φ, sγ = max(1 − 0.4·B/L, 0.6)
Net and Allowable Capacities:
qnet,ult = qu − γ · Dfqallow = qnet,ult / FOSQmax = qallow · A
Assumptions & References
- Soil is homogeneous, isotropic, and semi-infinite below the footing.
- The footing is rigid and located at a shallow depth (Df ≤ B).
- No inclined loads, eccentric loading, or groundwater table effects are considered.
- Depth and inclination factors are set to 1.0 (conservative baseline).
- For circular footings, B is treated as the diameter.
- A factor of safety of 2.5–3.0 is standard practice for most foundations (ASCE 7, Bowles).
- References: Terzaghi (1943); Meyerhof (1963); Das, B.M. — Principles of Foundation Engineering; Bowles, J.E. — Foundation Analysis and Design.